Long-Lived Electronic Coherences in Molecules.

We demonstrate long-lived electronic coherences in molecules using a combination of measurements with shaped octave spanning ultrafast laser pulses and calculations of the light matter interaction. Our pump-probe measurements prepare and interrogate entangled nuclear-electronic wave packets whose electronic phase remains well defined despite vibrational motion along many degrees of freedom. The experiments and calculations illustrate how coherences between excited states can survive, even when coherence with the ground state is lost, and may have important implications for many areas of attosecond science and photochemistry.

Molecular Engineering to Tune Functionality: The Case of Cl-Substituted [Fe(terpy)].

The properties of transition-metal complexes and their chemical dynamics can be effectively modified with ligand substitutions, and theory can be a great aid to such molecular engineering. In this paper, we first theoretically explored how substitution with a Cl atom at different positions of the terpyridine ligand affects the electronic structure of the [Fe(terpy)] complex. We found that besides the substitution at position 4', the next most promising candidate to cause substantial electronic effects is that where the side pyridine ring is substituted at position 5 (β).

Branching mechanism of photoswitching in an Fe(II) polypyridyl complex explained by full singlet-triplet-quintet dynamics.

It has long been known that irradiation with visible light converts Fe(II) polypyridines from their low-spin (singlet) to high-spin (quintet) state, yet mechanistic interpretation of the photorelaxation remains controversial. Herein, we simulate the full singlet-triplet-quintet dynamics of the [Fe(terpy)] (terpy = 2,2':6',2"-terpyridine) complex in full dimension, in order to clarify the complex photodynamics. Importantly, we report a branching mechanism involving two sequential processes: a dominant MLCT→MC(T)→MC(T)→MC, and a minor MLCT→MC(T)→MC component.

Excited-state dynamics of CHI and CHIBr studied with UV-pump VUV-probe momentum-resolved photoion spectroscopy.

We perform time-resolved ionization spectroscopy measurements of the excited state dynamics of CHI and CHIBr following photoexcitation in the deep UV. The fragment ions produced by ionization with a vacuum-ultraviolet probe pulse are measured with velocity map imaging, and the momentum resolved yields are compared with trajectory surface hopping calculations of the measurement observable. Together with recent time-resolved photoelectron spectroscopy measurements of the same dynamics, these results provide a detailed picture of the coupled electronic and nuclear dynamics involved.

Coherent Control of Internal Conversion in Strong-Field Molecular Ionization.

We demonstrate coherent control over internal conversion during strong-field molecular ionization with shaped, few-cycle laser pulses. The control is driven by interference in different neutral states, which are coupled via non-Born-Oppenheimer terms in the molecular Hamiltonian. Our measurements highlight the preservation of electronic coherence in nonadiabatic transitions between electronic states.